How to Build Event-Driven Apps Using AWS EventBridge and NestJS

Event-driven applications are becoming increasingly important in contemporary software development. They allow systems to respond to incidents quickly and expand as needed.

In this article, I will demonstrate how to create a similar application using AWS EventBridge and NestJS. These tools collaborate to assist in building scalable, reliable, and easy-to-manage systems that seamlessly integrate with AWS services.

We will walk you through setting up AWS EventBridge, incorporating it with NestJS, managing events, and implementing recommended practices for faults, retries, and scalability

Table of Contents

What are Event-Driven Apps?

Event-driven applications respond to system or external events. These systems separate those who provide information from those who consume it, increasing scalability and adaptability over traditional request/response models. In such systems:

Producers emit events when certain actions occur (e.g., user registration).
Consumers listen to these events and perform corresponding actions (e.g., sending a confirmation email).

These systems shine in environments where real-time reactions and high scalability are required, such as in microservices architectures, IoT systems, and large-scale enterprise applications.

Why AWS EventBridge & NestJS?

AWS EventBridge is a serverless solution that simplifies the development of event-driven apps. It receives, filters, and broadcasts events from various services and third-party applications, automating traffic routing between the start and destination points for easier integration of multiple AWS services.

NestJS is a powerful framework for creating scalable, easily maintained applications. It provides a solid foundation for interfacing with AWS services like EventBridge using dependency injection, decorators, and TypeScript.

Combining these technologies enables developers to create scalable event-driven architectures, leveraging the power of AWS services along with the structure and maintainability of NestJS.

Setting Up AWS EventBridge

To use AWS EventBridge, first, create an AWS account and connect to the AWS Management Console. After logging in, locate the EventBridge platform.

Creating Event Bus and Rules

Event Bus: AWS EventBridge has a pre-set event bus, but customers can design their own to manage events from multiple sources.

Event Rules: Rules screen events and route them to the appropriate destinations.

Integrating AWS Services

AWS EventBridge supports various AWS services and external applications. You can integrate it with services like AWS Lambda for processing events serverlessly, SNS for broadcasting messages, and SQS for reliable event queuing.

Building a NestJS Application

To set up a NestJS application that interacts with AWS EventBridge, create services in NestJS to handle the business logic for event-driven actions.

Testing and Debugging

Write unit tests for each service to ensure functionality, using tools for testing and mocking AWS SDK to simulate EventBridge.

Monitoring with AWS CloudWatch

Utilize AWS CloudWatch to monitor event flows, failures, and retries. Set up metrics and alerts to troubleshoot any issues that arise in the event-driven system.

Best Practices

Focus on scalability, idempotency, and using Dead Letter Queues (DLQs) to handle failed events.

Integrating AWS EventBridge with NestJS allows you to build a powerful event-driven system that adapts to your application’s needs, ensuring efficient responses to events while maintaining scalability and flexibility.